My file is no longer password-protected.
You may have saved the file in a different format. For example, if you save your file as a Web page, passwords are removed. Although most aspects of your file are maintained when you save it as a Web page, it does not maintain password protection or enable you to create a password after you've created the Web page.
To preserve a password, save a copy of your file in its original format before saving it as a Web page.
The password I typed doesn't work.
Passwords are case-sensitive. Check to see whether the CAPS LOCK key is on, or retype the password to make sure that you didn't mistype it.